1. Field of the Invention
The invention relates to a magnetic field generating assembly and a method of constructing such an assembly.
2. Description of the Background Art
Magnets for generating high strength magnetic fields are used in a wide variety of applications including nuclear magnetic resonance (NMR). In the case of whole body imaging and the like, large magnet structures are required leading to very high costs. One of the significant reasons for these high costs is the need to provide superconducting material which historically has comprised copper cooled to liquid helium temperatures. This requires the provision of efficient cryostats and the like.
Low temperature superconductivity is difficult to maintain in large structures because of the small "packets" of heat that can raise the temperature of the conductor above the critical temperature for superconductivity. Elegant forms of the conductor design have been created to minimise electromagnetic sources of heat arising within the conductor during operation. However, as magnets become larger, and the systems in which they are incorporated more complex, support engineering to avoid macroscopic heat pulses from structural movement and heat leaks from the environment become costly.
Recently, relatively high temperature superconducting materials have been discovered. By "relatively high temperature" we mean temperatures higher than for example liquid nitrogen temperatures (77K) at which the materials superconduct.
In order to duplicate conventional approaches using coils of wire it would be necessary to produce long lengths of wire made from the high temperature superconducting materials. In practice, this is not possible since the high temperature materials only carry useful current densities if they are made by very specialized fabrication processes, particularly those that apply to thin films. There would be no possibility of providing many kilometers of thin film like material to wind the magnet conventionally.